Electronic switch



July 28, 1953 PQJEANLIN 7, 7

ELECTRONIC SWITCH Filed June 11, 1948 3 Sheets-Sheet 1 July 28, 1953 P. JEANLlN 7 ELECTRONIC SWITCH Filed June 11', 1948 s Sheets-Sheet 2 July 28, 1953 Filed June 11, 1948 III" 'IIIIW P. JEANLIN ELECTRONIC SWITCH 5 Sheets-Sheet 3 Fatented July 28, 1953 UNITE 1) STAT-ES PATEN OFFICE- 2,647,172 ELECTRONIC swi'lrdfi? Pierre Jearilin; "ParisfFranee,-assignoi 'to"S6ciete Le Teleampliphone, Paris,'Ffa.1ice Alip'li'catith'imn 11'', 1948, salami-22232? 11' Claims? (01. 179 110 r 1 I The inventionre1atesf'tofan electronic sw'it'eh I which operates afterthefashi'on of an elleoti'icaPf reciprocating device and is constitutechbwthe" combination of two three-grid valves-which'form osei'llato'rs' but ofwhich'only 'one-canoscillate'at a time;a first grid of each valye'bei'ng connected? to the second grid'"of the other talvefwith-wwo triddej's, biased tocut be; whichdi'rec't' the pan trollin'g' impulses 'towards' the thirdfgrid" ofthe oscillator in'osci1l'ation"at this instant." U The electronic 'switch' in"accordance with -the invention may be employed forvariouspurposest The invention contemplates more" especially; but notexclusivelyyits application totwo-wayilondspeaker telephone installations not-using ma'nnai switching for the reversal ofthe -difectiomof'- convers'ation,-' the supply voltage whichis causecl to appearbr disabpea'r-by the -reciprocatory sys tenobeing obtained naturally-by thenegatiye volt; age resulting from the-rectificatiorf 0mm 'oscil lating high frequency: I V I In "United states copendingapplieationiSeria-l N o. 2%;445ffi1ed May 21 1948;for-Improvements in Loud-Speaker Telephone installations,f now U.- S. Patent 1 N o 25459176,:- apparat'us-has 'been describe'd'based upon the principleof one-or-twof amplifiers -'1oc'at'ed in each and bloclzfed, the' j blocked 'amb'lifierunblocking-itself; automatically upon theappearance'ofthemodulation after hai ing'- blocked the; free amplifien Y This -apparatusf works correctly in practice; but with a timeton stant'which is notalways "negligible: Moreover} the i blocking and tin-blocki-ng remairr*subject to the variatio'nsofiam irlit ude of the modulation and f therem'y result from this jerksand irregularities" E,

during the conversation if the speakers raise "or j lower the voice" and 'appro'a ch -towarlls-or ieede' I from' the microphones. These phenomena limit the uses' of this "apparatus. In 'order to'remdythis; intensity regulatin'g systems-have been -'in-' 4 trodiiced which makeithe apparatus apbfeciably more complicate'dz It'has anpe'areif prefrabl' fio withdraw theblocking and nnb looking frfii the influence of the modulationfonlcethe ,latter ha's fulfilled fits initial function of 'blocki'ngmr" un blocking caused by'- the" first syllable --spokh "in 7 front of o'ne-of-the microphones. The vention" relates to an electronic-swam mits this result to be'attainedan d which tions as an electricalreciprocatingdeviceifal- 50 ternately unblocking "the amplifiers for ope a tion. I

Such'a switch offers; in this case, theadvmi tage of being-veryrapid;'as- 'the arrangemn about to be described "does not 'reqn-ireconxp1ex-- v v. t of the nature t'es the" switch fas apbliedftoa i -stationin a two line lolid speaker telephone' in rid Gi a cond nser canes ilariable 'res isttanbe R a indi ated m gur the oscillatork high? frequency tefisionydter mes; at 'thefterm inals If thereri's "introduckiinto the circuifl'offthe wr R th a pea and o afnegativ tensionmyf-f tension {is th isjaropaition as for efiecttopolarize-th queri y tension anti C, the said polarization is suflicient for blocking the oscillation which is arrested and recovers only after discharge of into R.

It is advantageous to utilize this phenomenon by causing the valve L to function after the manner of a blocking oscillation that is to say by giving to R. and C such values that the consequence of discharges from 0 into R superposes on the high frequency oscillation (for example 20 megacycles) a low frequency oscillation of relaxation (for example 12.5 kilocycles-saw tooth frequency). In this manner, if the impulse received is feeble, it is certain that at the end of a very short time the oscillator L will be blocked. In practice, the phenomenon of blocking is obtained by using a condenser C of 500 pf. (1 pf.=- ;rf.) for a resistance R of 250,000 ohms.

In these conditions, if a small negative tension is applied to a grid, other than GI, for example to G2, as by an appropriate switch I, this will cause the oscillation to disappear.

If a system such as that in Figure 2 be now considered, two high frequency oscillators L and L are concerned instead of one. In each of these, the grid G2 (or G 2) is connected to the grid G l (or GI) of the other by a coupling resistance RI or R l itself uncoupled by a condenser CI or C l. In practice it is necessary to eliminate the alternative component between GI and G 2 (or G2 and G I)' and for the purpose the choke resistance of RI (or R I) is used, the high frequency component on G 2 (or G I) being eliminated to earth by the uncoupling condenser CI (or CH In effect, a filter is provided.

If it be assumed that the valve L oscillates, it will be seen that the grid G 2 of L will be polarized negatively by the tension rectified at the terminals of R l; L therefore cannot oscillate as has been shown above. If the first oscillator L ceases, the oscillator L is free immediately and polarizes in its turn the grid G2 of L, preventing it oscillating even if the normal conditions of oscillation are otherwise re-established. Therefore, one only of the two valves can oscillate at one and the same time.

In effect, the principal role of each valve L or L is to furnish a negative tension to the middle grid of the other.

It sufiices then to send in turn an impulse of suitable polarity to one of the electrodes of the valve in action for stopping its oscillation and for working the other valve which maintains the blocking of the first; the same result is evidently obtained by applying a negative tension to the third grid G3 (or G 3) of each valve.

In Figure 3, an electronic switching arrangement in accordance with the invention is realized by the addition to the two valves L and L of two triode valves LI and LH. The circuits are as follows: the grid GI of L is connected, as in Figures 1 and 2, on the one hand to a variable resistance R. and through a condenser C to an excitation winding EI, and on the other hand through a resistance R I to the grid G 2 of L it is the same for GI and G2. Moreover, GI is connected in shunt from the point A to the grid G 4 of NI through a charge resistance R2 and G2 is connected in shunt from the point B to the grid G4 of LI through a second charge resistance R 2. On the other hand, the impulse which controls the switch arrives at I and is transmitted to G4 through a condenser C2 and to G 4 through a condenser C 2. Finally, the connection of the triodes LI and DI in relation to the late, L1 is on the contrary free.

4 valves L and L is that of a standard stage amplifier. The anode of LI is connected through a condenser C3 to the grid G3 of L, and the anode of UI is similarly connected through a condenser C 3 to the grid G 3 of L The operation of the switching system is as follows: the triodes L1, L 1 are over polarized by the oscillators L, L and direct the control impulse in turn to that valve L or L which is in oscillation. In practice, if a positive control impulse arrives at I and if it is supposed that L is oscillating (L beng blocked) it results from the oscillation of L that L 1 is blocked by the negative tension applied to R2. As L does not oscil- The positive impulse arriving at I has no effect therefore upon the blocked L 1 but arrives at L1 which transforms it into a negative impulse, and transmits it to the grid G: of L. The oscillation of L then ceases immediately owing to over polarization.

On the other hand, the impulse which has been transmitted by the condenser C2 to the grid G4 of L1, returns, by shunt, to the grids G2 of L and G 1 of L through R 2 and B.

The operation is the same when L is oscillating and L is blocked. It will be seen therefore that the switching arrangement functions according to the principle of a to-and-fro electric system, the impulse being transmitted automatically to the oscillator unblocked at the moment for immediately blocking it whilst the other is unblocked.

An important application of the switching arrangement is that of blocking and unblocking alternately amplifiers in a two-way loud speaker telephone installation.

A first example of application in the case of a four line installation, is illustrated in Figure 4. For simplicity, a single line is used to represent the two lines of each way and circles represent the different valves employed.

Each station P (or P1) comprises a microphone M (or M and a loud speaker HP (or HI). Between M and HP is interposed the usual amplifier consisting for example of two valves L2 and L3, and between M and HP is inserted a similar amplifier L zL 3. In shunt between M and L2 there is an amplifier L6 and between M and L2 there is in shunt another similar amplifier L16. The installation comprises, moreover, two oscillator valves L and L of the type indicated above and forming with the valves L2 and L 2 the switching means. L6 is connected to the valve L of the switching arrangement by a rectifier D1. Similarly, L 6 is connected to the valve L of the switching arrangement by a rectifier D 1. On the other hand L and Lrz are directly connected together as also are L and L 2. Finally, between 10 and HP and similarly between L 3 and HP there are connected in shunt rectifiers D2 and D2 which are connected also with La and L 6. The rectifiers DI, D 1, D2, and D 2 have a polarity as shown in the drawing,

With this arrangement, the operation of the installation is as follows: If it be assumed that L procures the negative tension which blocks L2 and L it follows that L 2 is not blocked since L does not oscillate and speech passes normally from M to HP, that is to say from P to P.

If, now, P wishes to speak, the microphone M is impressed and the valve Ls sends an amplified modulation, rectified by D1, which stops the oscillation of L. At this moment, L2 is unblocked and L can then oscillate. The oscillator L 2 is then blocked as well as L the blockage of which ismaintained; Speech is; then transmitted freely; from Mto HP thatisto say from'Plto P whilst": L 2 prevents P from speaking. At thesametime; Dz furnishes a cut-01T- polarizationito (L16 which prevents the influence .of HP eupon. L and this. sendsby D 1 the corresponding impression to -L At thesametime, also, L6 isrgstrainedto avoid a the permanent sending. of a tension to D1, the/ purpose of this being to accelerate the-..unblockqing. WhenM becomes silent, D2 frees-L e'and M cantakeover the -speecch by=unblocking in the samemanner L z-whilst restrainingvLe andL e through D 2- As will be seen,- the rectifien Dz' plays a double role: First, it withdraws Ls 'from the modulationaction emitted by M untilLe -fu 1fi1ls'-=its purposeand has unblocked L2 moreover, it prevents the valve L16 from transmitting to the rectifier D 1 the modulation: arisingfromthe --action of H P upon M (Larsen efiecth' Second, the role of D2 is analogous in the-otherdirection asitsup' presses the Larsen effect atithe-station-Pw There results from this -arrangement-- the -very great practical advantage thatitispossible; -wi-thoutinconvenience, to mount M-;-and-I-P,=-as-' well-as M and HP -in a single box whicn considerably simplifies v the installationat each station;

In FigureB there is illustrateda practicalformof the improved-switching means: This com-- prises -two heptodes preferably --of' the 'type ECI-IZL- which osci-llate--wi-th--high frequency. These valves really consist of-a triple grid-and a triode combined, with--a cathode common to twoanodes An and Am-(An and-An i).

Assume that-the valve L plays the part "ofthevalve L in the precedingfigures, the triple grid of L10 oscillates --with-high frequencyandblocks L 10 by polarization; of G from R. The same tension alsoblocksLz, Figures l and -5 The positive tension from D1 (unblocking-im-- pulse) is given by the rectification of the modu lation-coming from-Leand-rectified by-D1, and" c it is transmitted tothe grid -Grof the triode--ele-" ment. (This latter -corresponds-to the valve'Li [or- L 1] of Figure 3.) This positive tensionhas it for effect to augment-the-anode-currentof-thetriode--element.- The circuit-is closedagainby' the cathode common-tothe triode' andtripl-e gridelements by the-resistance-Rro; 'Ihetension atthe terminals of'Rw augments-,=-the same with"- the polarization of G1 and G3,- and the oscillation-' is arrested This blocking results-'in' theun blocking of L2 and L 10,- whereupon-the latter'is put into oscillation and maintainsthe blocking of L10 primed by-D1. P can-then-speak to-P but-the opposite way-is blocked; Thefunct-ion ing-of L 10 is exactly similar;

In'FigureS, the impulses-have-tWo-different origins (Di and D 1) and not-a single origin l as in Figure 3. I Also,- for avoiding "the employment of -a fifth grid, a positive-impulse'is sent tO'G4 which comes tothe same thing;

It will -beunderstood from the foregoing-"that. the time constants of theblock-ing and unblocking circuits are determined-insuch manner that between twosyllables "firm-10111106121 by one of the l speakers the other can take over thespeech (this will be the case for example with thecircuits of D2 to L's and of D zto L6, in theexample illustrated; in Figure 4-).

Another.v example. of application "of i the electronio switching arrangementaccording-to the invention will nowc'beugiven. This-is the case-of an; ordinary telephone installation with two lines.;- Figure. 6 represents very diagrammatically one of the stations, the; lines, being. represented-,.:for:: greater simplicity, by a singles-drawing linegzthec different. valves by. circles and .1the.ISWitCh,.bya. a square Xi. The second station :may Ebi .of' .anyc: suitable type. It will be seen'thatthe elementsrs are the-same as in Figure 4 with;the .exception of. the vmicrophone:v M and .z'loudespeaker. H12 Which are replaced .by a transformer Tiwhich-a. permits of the sending. over the. two-wires, of;':- the system Z modulations emitted by M and ofi? the. arrival at the loud-speaker :HP-of module;- tions coming over the two wires of the system-1Z3 In the present case, however, the communications being always in the same direction upon each line, it is-possible to replace the well-known diiferem tial transformer. used by the French Telephone- Administration bya simple adaptation transformer of three windings; one of these bing connected to the system'Z and the other two-" respectively to L3 and L 2 (that is-to-sayato M and-to HP). The operation is the same as-that of the arrangement-in Figure 4; In Figures4 i and 6, the arrows indicate the path followed-by the impulses between the different units.

The result of the foregoing isthat a switching arrangement means conforming with the-inven-'-'-- tion gives to an installation in which it is em---- ployed the following advantages:

1. A single amplifierworking atone timey'tl'ie power is not limited and-the loud-speaker-can be put in the same box asthe microphone.-

2. The amplifiers having no intermediate posi-*- tion between blocking and unblocking (all 'or nothing) there is no distortion due to variations of polarization no more than'there is variation of power during audition;

3. The use or" independent and regulatable am plifiers for procuring the blocking and unblock ing tensions permits of' precise regulation of the. throwing out of the inversion and preventsthe superposition of modulations of one wayupon'; the other.

What I claim is:

1. An electronic switch comprising in combination a pair of electronic valves respectively, having an anode, a cathode, and a plurality of grids, a control winding connected to the anode, and an oscillating circuit including a condenser for coupling, said control'winding through Isaid 1 condenser to one of said grids, a tappin'gpoint.

between said condenser and said one grid, a re-: sistance having one terminal connected to ground and another terminal connected to said tapping point, and a second resistance connecting said tapping point and thereby said .one grid in one of said valves with a second grid in the other of said valves, each of said connected second resistances and second grids having a junction point therebetween with a condenser connecting, said junction point to ground.

2. An electronic switch comprising two'pentodes each having a cathode, an anode and a first, second and third grid, the first grid' of each? pentode being connected with the second 'grid '1 of the otherthrough a resistor, thefirstgrid'of f each tube being connected through a resistor to ground, the second grid of each tube being con-' nected through a condenser to ground, the anode. of each tube. being inductively coupled with'the' first grid of its own tube through a grid input'", circuit, there-being a condenser in' series between said input circuit and said-first grid.-

3. An electronic switch comprising a *pairof' vacuum tube oscillators respectively havinggat' 1 least twogrids; and a biasing resistonconnected'" to one of said grids for developing a negative potential in response to operation of the oscillator of which said one grid forms a part, the other of said grids being a control grid, a pair of circuits respectively operable to apply the negative potential developed by operation of one of said oscillators to the control grid of the other of said oscillators, each of said circuits including means for filtering the alternating components therefrom.

4. In a two-way communication system having at least a pair of stations respectively provided with a transmitter and a receiver and transmission lines connecting each transmitter at one of the stations with a receiver at the other of the stations, the invention which comprises the combination with the transmission lines of an electronic switch comprising a pair of electronic valves respectively having an anode, a cathode, and a plurality of grids, a control winding connected to the anode and an oscillating circuit including a condenser for coupling said control winding through said condenser to one of said grids, a tapping point between said condenser and said one grid, a resistance having one terminal connected to ground and another terminal connected to said tapping point, and a second resistance connecting said tapping point and thereby said one grid in one of said valves with a second grid in the other of said valves, each 1 of said connected second resistances and second grids having a junction point therebetween with a condenser connecting said junction point to ground, each of said lines having an electronic amplifying valve therein, each of said electronic switch valves being connected respectively to a difierent one of said amplifying valves, and means under the control of the transmitter of each station for generating a blocking potential and applying it to one of the grids of the electronic switch valve connected to the amplifying valve in the line to which said transmitter is connected.

5. The invention claimed in claim 4 wherein there is provided a transformer for coupling the transmitter and receiver of one of said stations into the system.

6. In a two-way communication system having at least a pair of stations respectively provided with a transmitter and a receiver and transmission lines connecting each transmitter at one of the stations with a receiver at the other of the stations, the invention which comprises the combination with the transmission lines of an electronic switch comprising a pair of electronic valves respectively having an anode, a cathode, and a plurality of grids, a control winding connected to the anode and an oscillating circuit including a condenser for coupling said control winding through said condenser to one of said girds, a tapping point between said condenser and said one grid, a resistance having one terminal connected to ground and another terminal connected to said tapping point, and a second resistance connecting said tapping point and thereby said one grid in one of said valves with a second grid in the other of said valves, each of said connected second resistances and second grids having a junction point therebetween with a condenser connecting said junction point to ground, each of said lines having an electronic amplifying valve therein, each of said electronic switch valves being connected respectively to a different one of said amplifying valves, each transmitter having an auxiliary amplifier and a rectifier connecting it to one of the grids of that electronic switch valve which is connected with the amplifying valve in the line to which said transmitter is connected.

7. The invention claimed in claim 6 wherein each of said lines has a rectifier connected thereto at a point between its connection to the receiver and the amplifying valve in such line for supplying a rectified control voltage to both of said auxiliary amplifiers.

8. In a two-way communication system having a pair of stations respectively provided with a transmitter and a receiver and transmission lines connecting each transmitter at one of the stations with a receiver at the other of the stations, the invention which comprises the combination with said transmission lines of amplification means in each of said lines for amplifying signals being transmitted thereby, a pair of oscillation generator means including means connecting each of said generator means with the other whereby only one of said generator means may oscillate at any given time and whereby the generator means which is oscillating produces a biasing control voltage for blocking the oscillation of the other, and means inter-connecting said pair of lines and said pair of generator means whereby the biasing potential produced by one of said generator means is effective to render the amplification means in one of said lines inoperative, and the biasing potential produced by the other of said generator means is effective to render the amplification means in the other of said lines inoperative.

9. In a two-way communication system having a pair of stations respectively provided with a transmitter and a receiver and transmission lines connecting each transmitter at one of the stations with a receiver at the other of the stations, the invention which comprises the combination with said transmission lines of amplification means in each of said lines for amplifying signals being transmitted thereby, a pair of generators respectively operable to generate high frequency oscillations and including means for developing a biasing potential in response to oscillation thereof, means inter-connecting said generators for applying the biasing potential of the generator which is oscillating to the other to prevent oscillation of the other so that only one of said generators is in oscillation at any one time, means connecting each of said amplification means with one of said oscillators whereby the biasing potential produced in response to oscillation thereof is effective to render the amplification means connected thereto inoperative, and a control means for each of said lines responsive to the impression of a signal to be transmitted over such line for preventing oscillation of the generator means connected to the amplification means in such line to thereby render said last-named amplification means operable t amplify the signal to be transmitted.

10. The invention claimed in claim 9 together with a means associated with each of said amplification means in one of said lines and responsive to the amplification of a signal thereby for preventing operation of the control means for the other of said lines.

11. An electronic switch comprising a pair of vacuum tube oscillators respectively having at least two grids, and a biasing resistor connected to one of said grids for developing a negative potential in response to operation of the oscillator of which said one grid forms a part, the other of said grids being a control grid. and a PIERRE J EANLIN 5 References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 10 Geiger May 9, 1939 Bertnolli et al June 27, 1939 Number 10 Name Date Koch Apr. 30, 1940 Herrick May 12, 1942 MacDonald Aug. 15, 1944 Donaldson Dec. 26, 1944 Baird Feb. 27, 1945 Nicholson, Jr Sept. 30, 1947 Cleeton Nov. 2, 1948 Mittelmann Nov. 9, 1948 Wild et a1. Dec. 28, 1948 Cotton Oct. 18, 1949 

